This invention relates to a control method for controlling the operation of an air conditioning system for use in a vehicle, and more particularly to a control method of this kind which affords selection of desired one of a driveability-preceding control mode and a cooling capacity-preceding control mode to be applied to control of the system.
In air conditioning systems for use in vehicles, the compressor is driven by the engine of the vehicle. Therefore, the operation of the air conditioning system causes an increased load on the engine, which results in a drop in the output of the engine. Consequently, the engine can show degraded accelerability or output shortage during acceleration or during high load operation. To avoid such phenomena, it has conventionally been employed to interrupt the operation of the compressor of the air conditioning system or control the delivery quantity, i.e. per-rotation volumetric throughput of the compressor to a minimum value if it is a variable delivery type, during acceleration or high load operation of the engine, so as to avoid application of a large load on the engine on such an occasion, as proposed by Japanese Utility Model Publications No. 47-981 and No. 51-23163. On the other hand, some air conditioning systems have employed a cooling capacity-preceding control method in which the above-mentioned interruption of the operation of the compressor or reduction of the delivery quantity of the compressor to a minimum value is effected only when the thermal load on the air conditioning system such as the car compartment temperature becomes less than a predetermined value. Such a cooling capacity-preceding control method has been proposed by Japanese Provisional Patent Publication No. 57-58032.
However, according to these conventional control methods, the control of the air conditioning system is carried out irrespective of the driver or passenger(s)'s will or desire. Therefore, those who make much of the cooling capacity, preferring that a comfortable riding space should be obtained even if the driveability is somewhat sacrificed, will feel uncomfortable when the driveability-preceding control method is applied wherein the compressor of the air conditioning system is interrupted or has its delivery quantity reduced to a minimum value. On the contrary, those who make much of the driveability, preferring that satisfactory accelerability or slope-ascending ability of the engine should be maintained even if the cooling capacity is somewhat sacrificed, will feel disatisfied when the cooling capacity-preceding control method is applied in controlling the air conditioning system. Thus, there are contradictory desires of the users.